n = int(input())
cs = input()

print(cs[:cs.count('R')].count('W')) n = int(input()) n int(input()) int input() input cs = input() cs input() input print(cs[:cs.count('R')].count('W')) print cs[:cs.count('R')].count('W') [:cs.count('R')].count [:cs.count('R')] cs :cs.count('R') cs.count('R') cs.count cs count 'R' count 'W' n = int(input()) int(input()) n cs = input() input() cs
n = int(input())
cs = input()

print(cs[:cs.count('R')].count('W'))
